Creep annealing and a multiple pin fixture for use therein

ABSTRACT

A plurality of fixed support pins extend upwardly from a base in predetermined spaced relation and to individual heights corresponding in composite to the design contour for the lower surface of a workpiece, and a plurality of independent movable pins extend downwardly through individual opening in a holder and are weighted to exert a suitable force upon the upper surface of the workpiece to effect creep therein during a heat anneal time cycle for the workpiece and thereby accurately shape the workpiece according to the predetermined contour in the general plane of the lower side thereof.

United States Patent [1 1 Gauthier [111 3,745,805 [451 July 17, 1973 CREEP ANNEALING AND A MULTIPLE PIN FIXTURE FOR USE THEREIN [75] Inventor: Roland A. Gauthier, South Milwaukee, Wis.

[73] Assignee: Ladish Co., Cudahy, Wis.

[22] Filed: Aug. 27, 197-1 [21] Appl. No.: 175,502

[52] US. Cl 72/364, 72/385, 148/131, 266/25 [51] Int. Cl B21d 11/00 [58] Field of Search 72/342, 364, 371, 72/385; 29/1568 B, 156.8 P; 148/115, 130,

[56] References Cited UNITED STATES PATENTS 663,156 12/1900 Budke ..72/364 Primary Examiner-Lowell A, Larson Attorney-Andrus, Sceales & Sawall [57] ABSTRACT A plurality of fixed support pins extend upwardly from a base in predetermined spaced relation and to individual heights corresponding in composite to the design contour for the lower surface of a workpiece, and a plurality of independent movable pins extend downwardly through individual opening in a holder and are weighted to exert a suitable force upon the upper surface of the workpiece to effect creep therein during a heat anneal time cycle for the workpiece and thereby accurately shape the workpiece according to the predetermined contour in the general plane of the lower side thereof.

9 Claims, 4 Drawing Figures PAIENIED L 7 SHEEIIUFZ INVENTOR ROLAND A. GAUTHIER BY XMW ATTORNEYS P'ATENIEBJUL v ma sum 2 or z INVENTOR ROLAND A.GAUTHIEF\ BY I ATTORNEYS CREEP ANNEALING AND A MULTIPLE PIN FIXTURE FOR USE THEREIN BACKGROUND OF THE INVENTION This invention relates to creep annealing and a multiple pin fixture for use therein.

The invention has been particularly applied to the straightening of thin forged workpieces such as turbine blades of titanium alloy to facilitate inspection and sub sequent machining thereof.

There are many variables in forging workpieces of this nature whereby the forged workpiece may vary in shape due to tolerances in die mating, wear of the dies, stresses resulting from metal flow and stresses resulting from temperature gradients. As a consequence neither side of the workpiece has the desired contour originally intended, and the workpiece may be warped out of the original plane.

It has been the custom to anneal such workpieces to remove residual stresses prior to machiningand when this is done a certain amount of warping may be encountered depending upon the manner of supporting the workpiece during anneal.

Some attempt to avoid such distortion during annealing by confining the workpiece in heated dies of the desired final shape. Thispractice does not accommodate variations in thickness from that of the die cavity and may introduce additional stresses from uneven cooling.

workpieces which vary from the original intended plane become difficult to machine to final dimensions.

SUMMARY OF THE INVENTION The present invention utilizes creep during the annealing of the workpiece to return it to an accurate shape on one side (the bottom side when supported for annealing) and leaves the opposite (top) side substantially free to take its level accordingly.

This leaves any irregularities in thickness over that of the original design to be taken care of by machining on the top side. y

In carrying out the invention the workpiece is supported during annealing on a plurality of fixed upstanding pins positioned at suitable intervals to prevent sagging of the workpiece therebetween, and having their upper ends located according to the design contour of the bottom side of the workpiece.

A complemental set of pins rest vertically upon the top of the workpiece at intervals corresponding to the spacing of the supporting pins. These upper pins are individually weighted to apply pressure to the corresponding areas of the workpiece, thereby effecting creep therein.

Prior to annealing, the workpiece may engage and be supported only by a few of the pins, and during annealing the creep of the workpiece will cause the same to re-establish the desired design plane of the bottom side by engaging each of the pins.

The upper pins are held in place by a plate which has holes therein through which the pins extend freely for individual movement in accordance with the creep of the workpiece.

The plate is supported at its corners either by posts extending upwardly from the base which supports the lower pins or by a few fixed depending pins resting on the workpiece at locations corresponding to upstanding pins supporting the workpiece.

A suitable lateral interlock is provided between the plate and the base and/or the workpiece.

BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment constituting the best mode presently contemplated for carrying out the invention is illustrated in the accompanying drawings in which:

FIG. 1 is a side elevation of an annealing fixture partially in section and with a workpiece therein prior to creep annealing;

FIG. 2 is a similar view showing the same after creep annealing of the workpiece;

FIG. 3 is an enlarged section taken on line 33 of FIG. 1; and

FIG. 4 is a similar section taken on line 4-4 of FIG. 2.

DESCRIPTION OF PREFERRED EMBODIMENT The bottom fixture illustrated in the drawings comprises a rigid base 1 to the top surface of which a plurality of spaced vertical pins 2 are welded.

The length of the individual pins 2 and the contour of the upper end surfaces thereof are such as to provide a general plane of support for the workpiece 3 corresponding accurately to the desired design plane for the bottom side of the workpiece.

The top fixture illustrated in the drawings comprises a substantially horizontal plate 4 having a plurality of holes 5 therethrough and supported by end posts 6 extending upwardly from base 1.

A floating vertical pin 7 extends freely through each hole 5 and rests upon workpiece 3 immediately above a corresponding pin 2.

The upper pins 7 are individually weighted as by weights 8 to apply pressure to the workpiece 3 in the areas of the individual pins to effect creep of the workpiece during annealing whereby the bottom surface of the workpiece will assume the contour designed for it.

The posts 6 are located relative to the workpiece to hold the latter against lateral thrust from its weight and- /or from the pressure applied thereon by pins 7.

The weights 8 may be made up of standard increments in the form of blocks which can be selectively added or subtracted for adjusting the amount of weight to be provided for each individual pin, depending upon the force needed to effect the desired creep in the corresponding region of the workpiece.

The maximum weight 8 to be applied to any pin 7 should be less than that which would brinell the workpiece. The minimum weight 8 to be applied to any pin 7 should be sufficient to effect the desired creep early in the annealing treatment, having regard to the section, time and temperature.

As a specific example for annealing, a turbine blade of titanium alloy steel maybe heated to approximately l,400 F. for a period of 4 A: hours.

In general the annealing time and temperature will depend upon the alloy and the maximum section or thickness of the workpiece, and is according to standard practices which have been established for annealing.

In the present instance the temperature must be within the creep range which generally lies between the elastic flow range and the plastic flow range.

By employing maximum weights 8 for pins 7 the creep movement of the workpiece will be completed early in the annealing cycle so that any stresses resulting from the creep will be removed during the subsequent portion of the annealing cycle and before cooling of the workpiece.

The lower ends of pins 7 may be contoured generally to correspond to the upper surface of the workpiece 3 in the region of contact of the individual pins.

The fixture and workpiece assembled as illustrated in FIG. 1 is placed in an annealing oven or furnace, not shown, wherein heat is applied thereto to raise the temperature of the workpiece to the desired creep range.

The annealing time will then effect the necessary creep to re-establish the plane for the bottom surface of the workpiece corresponding to the original design therefor.

The workpiece will thus be resting upon all of the pins 2 upon completion of the annealing operation and removal of. the fixture and workpiece from the oven or furnace.

One of the advantages in employing mating pins to support the workpiece and apply the necessary force thereto to effect the desired creep, lies in the general exposure of the workpiece to the atmosphere of the annealing chamber or furnance, thus facilitating reasonably uniform heating and cooling of the workpiece.

Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

I claim:

1. The creep annealing of a metal workpiece, comprising providing a contour support for one side of the workpiece corresponding to the design contour therefor, annealing the workpiece, and applying pressure during said annealing independently to a plurality of selected areas of the opposite side of the workpiece to effect creep thereof toward said contour support.

2. The creep annealing of a metal workpiece, comprising supporting the workpiece at a plurality of points in the design plane for the bottom surface contour thereof, annealing the same while so supported, and applying downward pressure upon said workpiece independently at a plurality of spaced pre-selected locations mating with a plurality of additional support points to effect creep of the workpiece at said locations andre-establish the design contour plane for the bottom surface of the workpiece.

3. The process of claim 2 wherein the creep is effected early in the annealing cycle and the subsequent annealing removes any stress in the workpiece resulting from said creep.

4. A fixture for creep annealing ofa workpiece, comprising means establishing a support plane for one side of the workpiece corresponding to the design contour for said side, and means to apply pressure to said workpiece independently at a plurality of points on the opposite side of the workpiece to effect creep of the same toward said first named means during annealing of the workpiece.

5. A fixture for creep annealing of a workpiece comprising a base, a plurality of workpiece supporting pins extending upwardly from said base with their respective upper ends individually disposed corresponding to the design contour for the bottom of the workpiece, and a plurality of upper mating pins adapted to apply downward pressure upon the workpiece.

6. The fixture of claim 5 and means to position said upper pins in vertical alignment with corresponding support pins and for free individual vertical movement in response to creep of the workpiece.

7. The fixture of claim 6 and a plurality of weights selectively applied to said upper pins.

8. The fixture of claim 6 and means to retain the workpiece against forces tending to displace the same laterally in the fixture.

9. The fixture of claim 6 in which said upper pin positioning means comprises a plate having holes therethrough receiving the individual upper pins, and means to support said plate above the workpiece. 

1. The creep annealing of a metal workpiece, comprising providing a contour support for one side of the workpiece corresponding to the design contour therefor, annealing the workpiece, and applying pressure during said annealing independently to a plurality of selected areas of the opposite side of the workpiece to effect creep thereof toward said contour support.
 2. The creep annealing of a metal workpiece, comprising supporting the workpiece at a plurality of points in the design plane for the bottom surface contour thereof, annealing the same while so supported, and applying downward pressure upon said workpiece independently at a plurality of spaced pre-selected locations mating with a plurality of additional support points to effect creep of the workpiece at said locations and re-establish the design contour plane for the bottom surface of the workpiece.
 3. The process of claim 2 wherein the creep is effected early in the annealing cycle and the subsequent annealing removes any stress in the workpiece resulting from said creep.
 4. A fixture for creep annealing of a workpiece, comprising means establishing a support plane for one side of the workpiece corresponding to the design contour for said side, and means to apply pressure to said workpiece independently at a plurality of points on the opposite side of the workpiece to effect creep of the same toward said first named means during annealing of the workpiece.
 5. A fixture for creep annealing of a workpiece comprising a base, a plurality of workpiece supporting pins extending upwardly from said base with their respective upper ends individually disposed corresponding to the design contour for the bottom of the workpiece, and a plurality of upper mating pins adapted to apply downward pressure upon the workpiece.
 6. The fixture of claim 5 and means to position said upper pins in vertical alignment with corresponding support pins and for free individual vertical movement in response to creep of the workpiece.
 7. The fixture of claim 6 and a plurality of weights selectively applied to said upper pins.
 8. The fixture of claim 6 and means to retain the workpiece against forces tending to displace the same laterally in the fixture.
 9. The fixture of claim 6 in which said upper pin positioning means comprises a plate having holes therethrough receiving the individual upper pins, and means to support said plate above the workpiece. 